Field of the Invention
The present invention relates to a piezoelectric material, in particular, a lead-free piezoelectric material. The present invention also relates to a piezoelectric element, a multilayered piezoelectric element, a liquid discharge head, a liquid discharge device, an ultrasonic motor, an optical apparatus, a vibratory device, a dust-removing device, an image pickup device, and an electronic apparatus each including the piezoelectric material.
Description of the Related Art
In general, piezoelectric materials are ABO3 perovskite-type metal oxides such as lead zirconate titanate (hereinafter referred to as “PZT”). However, since PZT contains lead as an A site element, its influence on environment is controversial. Accordingly, there is a demand for a piezoelectric material of a lead-free perovskite-type metal oxide.
Barium titanate is known as a piezoelectric material of a lead-free perovskite-type metal oxide. In addition, in order to improve the characteristics of a piezoelectric material, a material of which base composition is barium titanate has been developed. Japanese Patent Laid-Open No. 2009-215111 discloses a material having improved piezoelectric properties by replacing a part of the A site of barium titanate with Ca and a part of the B site with Zr. Such a material, however, has a low Curie temperature, such as 80° C. or less, and thereby causes depolarization under a high-temperature environment, e.g., in a car in summer, to reduce the piezoelectric properties. In addition, since the mechanical quality factor is low, depolarization tends to occur when an AC voltage is applied to.
Japanese Patent Laid-Open No. 2011-032111 discloses a material in which a part of the A site of barium titanate is replaced with Ca and further to which Mn, Fe, or Cu is added. Though such a material has an excellent mechanical quality factor compared to barium titanate, the piezoelectric properties are low to require a high voltage for driving the resulting element.